Process for producing pipe sleeves from mineral wool

ABSTRACT

The invention relates to a process for producing pipe sleeves made of mineral wool for insulating pipelines or for reducing the sound level in pipeline systems, comprising the following steps: providing a nonwoven web ( 11 ) made of mineral wool which is provided with an uncured binder, winding up the nonwoven web ( 11 ) on a winding mandrel ( 2 ) of a winder, curing the binder. Here, at least one reinforcing layer ( 12, 13 ) is provided before the nonwoven web ( 11 ) runs into the winder, in such a way that during the winding the said reinforcing layer becomes a constituent part of the pipe sleeve produced as a result.

The invention relates to a process for producing pipe sleeves frommineral wool according to the preamble of claim 1, and also to pipesleeves which contain a wound nonwoven web made of mineral wool with acured binder.

Pipe sleeves of this type are frequently used to insulate pipelines inorder to minimise energy losses, for example in heating andservice-water lines. The insulating layer of such pipe sleeves isgenerally produced by winding a nonwoven web made of mineral wool onto amandrel of a winder and, as explained in DE 35 36 174 C1, can have anadditional external lamination of a thin metal sheet. By means of thislamination, which is usually a thin aluminium sheet, an improvement inthe compressive strength of the pipe sleeve, in particular in the radialdirection, is conventionally achieved. Furthermore, the metal laminationalso provides a trickle guard against any loose fibrous materialpossibly present in the pipe sleeve.

Such conventional pipe sleeves for insulating pipelines have been triedand tested, but, in particular, the process step of applying the metallamination entailing a relatively great deal of effort and beingrelatively expensive. If, on the other hand, the metal lamination isdispensed with, then this is associated with the problem of a possiblyincreased accumulation of dust and, and the same time, a worsened feeland strength of the pipe sleeve.

In a further area of application, pipe sleeves of this type are alsoused to reduce the sound level in pipeline systems, for example ofheating installations (chimney systems) or ventilation systems. Here, itis in particular a matter of largely nullifying the sound energy of thegases flowing through, by the sound waves being reflected and absorbedin a suitable manner. To this end, the pipes and pipe systems carryinggas are provided in the region of the pipe sleeve with normallyempirically defined apertures, through which the gas can expand into thespace between the pipe and an external housing. Since this space isfilled with a packing of mineral wool, the gas oscillations andtherefore also the sound waves are damped effectively.

The sound-level-reducing effect is of course maintained only as long asthe mineral wool filling is present and substantially fills the spaceallocated to it completely. Since, however, mineral wool consists of alarge number of fibres bonded to one another by means of binders, thisinner bond can be dissolved, in particular in the case of mechanicalaction or else by the gas stream, so that individual fibres can migrateout of the bond. This should be prevented with regard to a decrease inthe sound-level reduction, but also because the fibre fragments must notbe expelled with the gases, in order to avoid an uncontrollablecontamination and pollution of the environment and, ultimately, alsorisks to health.

One example of such a pipe sleeve is explained in DE 31 44 193 A1. Thisknown pipe sleeve has an insulating layer of mineral wool, which isformed by a nonwoven web which, in the manner conventional in theproduction of pipe sleeves, has been wound over a winding mandrel which,after the mineral fibre pipe sleeve has been removed, leaves behind apassage opening for the pipe. In order to protect the pipe sleeve and,in particular, the outer circumferential surface against mechanicaldamage and therefore to avoid fibre fracture or fibre discharge, thisknown pipe sleeve is also given a sheath of a woven glass fabric. Thissheath also has a reduced diameter as compared with the insulatinglayer, so that the insulating layer is present in a somewhat compressedstate within the sheath, which achieves securing of the position andalso beneficial spring properties and improved mechanical integrity ofthe arrangement. This pipe sleeve has been tried and tested in practice;however, in order to produce this type of pipe sleeve, apart from theseparate production steps for the components, in particular the mountingstep for the insertion of the insulating layer into the sheath is alsorequired, which is complicated and presents problems, in particular inthe case of relatively large numbers.

The invention is based on the object of indicating a process forproducing pipe sleeves which can be carried out cost-effectively withlittle effort and, firstly, leads to pipe sleeves with improvedmechanical properties and/or, secondly, to pipe sleeves with mechanicalproperties which are approximately constant as compared withconventional pipe sleeves but have lower bulk densities.

From a process engineering point of view, this object is achieved by thefeatures of claim 1. This comprises the following steps: providing anonwoven web made of mineral wool which is provided with an uncuredbinder, winding up the nonwoven web on a winding mandrel of a winder,curing the binder, at least one reinforcing layer being provided beforethe nonwoven web runs into the winder, in such a way that during thewinding the said reinforcing layer becomes a constituent part of thepipe sleeve produced as a result.

Thus, according to the invention, it is possible to achieve animprovement in the mechanical properties, with an astonishingly lowtechnological outlay and without having to interrupt the conventionalproduction process and in particular the winding operation. Inparticular, the mechanical strength of the pipe sleeve may thus beimproved, as a result of which the risk of fibre breakage, for exampleunder external mechanical influences, can be reduced considerably. Theprocedure according to the invention is also suitable in particular forlarge-scale mass production, as a result of which pipe sleeves of thistype can thus be produced more economically.

Furthermore, as a result of introducing the reinforcing layer, specificcontrol of the strength properties of the pipe sleeve to be producedbecomes possible, so that appropriate adaptations with respect to thebulk density to different uses, etc., can be carried out in processengineering terms with particularly little effort, that is to say bulkdensity can be saved as a result of the reinforcing effect of thereinforcing layer or layers, in spite of maintaining the stability ofthe pipe sleeves.

Advantageous developments of the process according to the invention formthe subject-matter of the dependent Claims 2 to 7.

Thus, the at least one reinforcing layer can be applied to the nonwovenweb in such a way that it is wound up with the latter and, followingwinding, is present within the pipe sleeve. In this way, the mechanicalproperties of the pipe sleeve to be produced can be set specifically andimproved without the external appearance standing out from the priorart. In addition to the stabilisation of the pipe sleeve, it issimultaneously also possible to achieve a reduction in the bulk densityby means of suitable selection of the reinforcing material, so that areduction in the overall weight of the pipe sleeve produced may beachieved. Furthermore, the addition of the reinforcing layer to thenonwoven web to be wound up can be carried out without difficulty, evenon a large scale, so that great improvements with regard to the materialproperties can be achieved with only minimally increased effort onprocess engineering.

In this case, it is of further advantage if the reinforcing layercomprises a plurality of separate strips, which are each placed on thenonwoven web and then wound up together with the latter. In this way,the input of the reinforcing material can be controlled in a mannerwhich is particularly beneficial in terms of process engineering. Thesestrips can be deposited without difficulty at a desired, predeterminedpoint and in a desired relation to one another on the nonwoven web,which is normally brought up on a transport element, and are thenautomatically wound in together with the said nonwoven web.

As an alternative or additionally to this, it is also possible to addthe reinforcing layer to the trailing end of the nonwoven web in such away that it comes to lie on the outside of the pipe sleeve with theeffect of a lamination, as the last layer arranged over the entirecircumference. Therefore, an external sheath or lamination can beprovided, as already proposed in DE 35 36 174 C1 explained at thebeginning or DE 31 44 193 A1, but there can be arranged only with aconsiderable effort in terms of process engineering. According to theinvention, this effort can now be reduced drastically, since thecorresponding reinforcing layer is automatically wound around. Since thewinding operation is usually likewise associated with a certain amountof compression of the mineral wool material, according to the invention,a certain prestress of the mineral wool material with respect to thesheath of reinforcing material can be produced to the same extent as inthe prior art, so that beneficial spring-back properties and mechanicalcharacteristics of the final product can be achieved. By means of thereinforcing layer wound around the outside of the pipe sleeve accordingto the invention, reliable trickle protection can be provided, asmoother surface also being produced as well. A pipe sleeve formed inthis way may be handled more conveniently. Furthermore, a highermechanical strength of the pipe sleeve can be achieved cost-effectively.

In a further alternative or supplementary configuration, the at leastone reinforcing layer can be applied to the winding mandrel, before thenonwoven web is wound up, in such a way that it represents the internalsurface of the pipe sleeve determining the clear internal diameter ofthe pipe sleeve. Configuring the pipe sleeve in this way is advantageousin particular in the use for a sound level reduction in pipelinesystems, for example of heating installations or ventilation systems, sothat the cohesion of the bonded mineral water fibres can be maintainedreliably even under the action of a gas flowing through and, inparticular, a type of trickle protection against the emergence into thepipeline system of particles possibly nevertheless loosened can beprevented reliably. In other words, the abrasion, that is to say fibreabrasion, at relatively high air or gas velocities is intended to beprevented thereby. The “internal lamination”, formed in this way, of thepipe sleeve may be provided in this case cost-effectively and withlittle effort on process engineering.

It is particularly advantageous if a glass nonwoven, a woven glass fibrefabric, for example E-glass or the like, is used as reinforcing layer.These have proven to be advantageous in practical trials since, inaddition to a comparatively low bulk density, they have good mechanicalproperties and can be wound together with the nonwoven web withoutdifficulty.

Furthermore, before being provided for the winding operation, thereinforcing layer can be wetted with additional binder, by which means,following the curing of the binder, an improved bond in the mouldingproduced in this way can be achieved. This additional binder can forexample simply be sprayed onto the reinforcing layer supplied, withparticularly little effort on process engineering.

According to a further aspect of the present invention a pipe sleevemade of mineral wool as defined in claim 8 is provided, which isproduced by means of a process according to any of claims 1 to 7. Suchpipe sleeve shows the advantageous effects as mentioned above withregard to the method claims.

In particular, according to claim 9, a pipe sleeve made of mineral woolis provided for insulating pipelines, which is formed of a woundnonwoven web with cured binder and in which there is at least onereinforcing layer on the inner side of the pipe and/or enclosed at atleast part of the boundary between successive wound layers.

Preferably, the at least one reinforcing layer is enclosed within thewound layers. This can therefore serve as a type of “reinforcement”within the pipe sleeve, which means that the mechanical strength of thepipe sleeve can be improved. However, it is particularly advantageous touse these improved mechanical properties to reduce the bulk density ofthe pipe sleeve and thus to reduce the production costs. The pipe sleeveaccording to the invention is thus distinguished by an excellent ratioof volumetric weight to mechanical strength, being capable of productioncost-effectively to a great extent and on a large scale.

In this case, the reinforcing layer can comprise a plurality of separatestrips, which means that the mechanical properties of the pipe sleevecan be set specifically. In particular, a suitable balance between areduction in bulk density and an improvement in the mechanical strengthcan be produced in this way.

In another embodiment, as defined in claim 12, a reinforcing layer maybe provided in the form of a trickle guard being wound circumferentialaround the pipe sleeve. In this way, an improved surface can be producedon the circumferential surface of the pipe sleeve, which permits thepipe sleeve to be reinforced with respect to external mechanicalinfluences. Therefore, the risk of fibre breakage in the event ofimproper handling, etc. can be reduced substantially, so that dischargeof fibre can be avoided to the greatest possible extent. In addition,this sheath, serving as a type of “lamination”, of reinforcing materialsuppresses the discharge of fibre to a substantial extent and is felt tobe more pleasant and smoother during handling. This makes it easier tohandle the pipe sleeve according to the invention, for example duringinstallation. As compared with a thin metal sheet which, because of itsstiffness, can automatically be supplied exactly, this is not possiblewith glass nonwovens serving as a trickle guard, because of theirdeficient inherent stability, for which reason the process according tothe invention constitutes a simple and effective possible way of doingthis.

According to a further aspect of the invention, as defined in claim 13,a pipe sleeve made of mineral wool is provided for sound-level reductionin pipeline systems, in particular of low-temperature heatinginstallations (flue installations) or ventilation systems, the pipesleeve being formed from a wound nonwoven web with cured binder andhaving at least one reinforcing layer, which provides the inner surfaceof the pipe sleeve, determining the clear internal diameter of the pipesleeve. Therefore, the expansion space required for the damping of gasoscillations or sound waves continues to be available in the pipe sleeveand, at the same time, a type of trickle protection against particleswhich may have been loosened is provided. In practical trials, thisconfiguration has proven to be suitable in particular for absorbingpressure peaks in the gas flow, such as normally occur in heating orventilation installations primarily during start-up, since part of thecombustion noise is transported to the outside via the waste gas path.In particular, the requirements on the prevention of noise in buildingconstructions, which are laid down in DIN 4109 and Technical Note Noisecan therefore be met.

The reinforcing layer used is preferably a glass nonwoven, a woven glassfibre fabric of E-glass or the like, which exhibit the advantagesalready explained.

Moreover, the reinforcing layer may include particulate material, suchas infrared radiation absorbing material or heat shielding material inorder to improve the properties of the pipe sleeve according to theinvention.

Further, the reinforcing layer may include a foil material, such as aheat reflective foil containing a metal like aluminum.

The reinforcing layer may be treated with a biocide agent.

Moreover, the reinforcing layer may be provided with means for allowingseparation of wound layers in order to reduce external or internaldiameter of the pipe.

The invention will be explained in more detail in exemplary embodiments,using the Figures of the drawing, in which:

FIG. 1 shows a schematic view of a winder adapted according to theinvention;

FIG. 2 shows a front view of a pipe sleeve according to a firstembodiment produced by means of the winder according to FIG. 1;

FIG. 3 shows a front view of a second embodiment of a pipe sleeveaccording to the invention;

FIG. 4 shows the details of the supply belt of the winder during theproduction of the second embodiment of a pipe sleeve;

FIG. 5 shows a front view of a pipe sleeve in a third embodiment; and

FIG. 6 shows an exemplary application in a heating installation.

FIG. 1 shows, highly schematically, a side view of a winder 1, on whicha pipe sleeve 10 (cf. FIG. 2) according to a first embodiment isproduced. The winder 1 has a winding mandrel 2, onto which a nonwovenweb 11 made of mineral wool, supplied by a first supply belt 3, is woundin an intrinsically conventional manner.

In the illustration shown, the nonwoven web 11 has already beensubstantially wound on the winding mandrel 2, an inner reinforcing layer12 having been placed on the winding mandrel 2 before the start of thewinding operation and, in this way, in the course of the windingoperation, becoming an integral constituent part of the pipe sleeve 10to be produced.

In addition to this, the winder 1 contains a second supply belt 4, bymeans of which an outer reinforcing layer 13 can be supplied in such away that its leading end overlaps the trailing end section of thenonwoven web 11 such that it is also wound into the coil. As a result ofthe further rotation of the winding mandrel 2, the reinforcing layer 13is ultimately led around the entire periphery of the existing coil, andits trailing end overlaps its leading end in a manner that can be seenschematically from FIG. 2. The reinforcing layer 13 therefore comes tolie completely circumferentially around the coil and forms an outersheath or lamination around the latter.

In a following curing step, the binder in the moulding formed in thisway is cured and the latter thus becomes the pipe sleeve 10, from whichthe winding mandrel 2 is then withdrawn, so that ultimately the pipesleeve 10 is present in the shape that can be seen from FIG. 2.

FIGS. 3 to 5 show a modified embodiment of the invention, in which thereinforcing layer is introduced in the form of strips in the course ofthe winding operation. Thus, FIG. 3 shows a front view of a pipe sleeve20 according to a second embodiment of the invention. In this, areinforcing layer 22 is also wound in inside a nonwoven web 21. For thispurpose, in the manner that can be seen from FIG. 4, the reinforcinglayer 22 is placed on the nonwoven web 21 supplied to the winder 1 bythe first supply belt 3.

FIG. 5 shows a third embodiment, according to which a pipe sleeve 30 hastwo integrated reinforcing layers 32 and 33 in a nonwoven web 31. Thesehave been placed on the nonwoven web 31 separately from one another atspecific times before the winding operation.

The pipe sleeves 20 and 30 are configured in such a way that they canpreferably be used for insulating pipelines. Another method of using thepipe sleeve 10 is shown in FIG. 6. In this schematic illustration, aheating installation 40 has a heating block 41, a waste-gas pipe 42 anda flue 43, it being possible for the waste gases from thelow-temperature heating installation, formed for example as an oil orgas heating system, to be led to the flue 43 via the waste-gas pipe 42.

Interposed in the waste-gas pipe 42 is a sound-level-reducing device 44comprising a housing 45, which encloses a pipe sleeve 50 according to afourth embodiment but which corresponds to the pipe sleeve 10 with theexception of an outer reinforcing layer 13 which may possibly bepresent.

The pipe sleeve 50 contains a wound nonwoven layer 51 and also an innerreinforcing layer 52, which provides the inner surface determining theclear internal diameter of the pipe sleeve 50. This inner reinforcinglayer 52 is formed from an E-glass nonwoven and therefore has aperturesthrough which the gas stream can expand into the wound nonwoven layer51. Therefore, the pressure peaks occurring in particular duringstart-up of the heating installation 40 can be dissipated in the device44, reducing the sound level. At the same time, the reinforcing layer 52to the greatest extent prevents discharge of particles loosened by theaction of the flow into the waste-gas pipe 42 or the flue 43. As afurther protection against the flowing waste gases, it is possible for afine-mesh wire basket to be arranged in the inside of the housing 45, infront of the reinforcing layer 52.

The invention permits further approaches to configuration in addition tothe embodiments indicated.

For example, the reinforcing layer can also be provided in such a lengthand projecting both beyond the leading and beyond the trailing end ofthe nonwoven web in such a way that, in the course of the windingoperation, both the reinforcing layer forming the inner surface of thepipe sleeve and the reinforcing layer integrated within the woundlayers, and the reinforcing layer forming the outer sheath, are providedfrom one piece.

Furthermore, it is not absolutely necessary for the leading end of thereinforcing layer 13 to overlap the trailing end of the nonwoven web 11in the manner shown in FIG. 1; instead, the reinforcing layer 13 canalso be introduced into the winding operation immediately following thenonwoven web 11. The reinforcing layer 13 can, furthermore, also besupplied to the nonwoven web 11 from below.

The inner reinforcing layer 12 or 52 can also be placed on the windingmandrel 2 separately in advance; alternatively, it is also possible thatthis is likewise supplied by supply belts and wound around the windingmandrel 2 in a conventional way, the winding of the nonwoven web 11 or51 then following.

The length and width dimensions of the respective reinforcing layers inall the exemplary embodiments are selected in accordance with thedesired properties of the final product, so that, for example, areinforcing layer can also be designed to be sufficiently long that itoverlaps itself more or less considerably in the coil. However, thewidth of each reinforcing layer is preferably selected such that itcorresponds to the width of the respective nonwoven web, in order inthis way to permit the advantageous properties also to come into effectuniformly over the entire product.

Also, the reinforcing layer may include particulate material such asinfrared radiation absorbing material. As disclosed in WO 02/092528, asuitable IR absorbing and scattering material absorbs and scattersinfrared radiation with a wavelength in the 4 to 40 μm range.Preferably, the IR absorbing and scattering material absorbs 6-8 μm(1667-1250 cm⁻¹) infrared radiation. The IR absorbing and scatteringmaterial can include borate compounds, carbonate compounds, aluminacompounds, nitrate compounds and nitrite compounds. These compounds canbe alkali metal salts or alkaline earth metal salts. Borate compounds,carbonate compounds and alumina compounds are preferred. Suitableborates include lithium borate, sodium borate, potassium borate,magnesium borate, calcium borate, strontium borate and barium borate.Preferably, the borate is sodium borate (i.e., borax, Na₂B₄O₅(OH)₄.8H₂Oor Na₂B₄O₇.10H₂O) or colemanite (Ca₂B₆O₁₁.5H₂O). Suitable carbonatesinclude lithium carbonate, sodium carbonate, potassium carbonate,calcium carbonate (i.e., calcite, CaCO₃), dolomite (CaMg(CO₃)₂),magnesium carbonate (i.e., magnesite, MgCO₃), strontium carbonate andbarium carbonate. Preferably, the carbonate is calcium carbonate,dolomite, or magnesite. Suitable alumina compounds include hydratedalumina (Al₂O₃.3H₂O or Al(OH)₃) and alumina (Al₂O₃). ALCOA producesHYDRAL and B-303 particles of hydrated alumina.

Moreover, the reinforcing layer may include particulate material such asheat shielding material. Heat shielding material can be selected amongphosphorous compounds, such as alkaline-earth phosphate especially acalcium phosphate.

Calcium phosphates, especially the orthophosphate (Ca₃(PO₄)₂) and thepyrophosphate (Ca₂P₂O₇), are known to be refractory and these compoundshave melting points of 1670° C. and 1230° C., respectively. Thephosphorus compound may also be a compound chosen from the followingcompounds:

ammonium salts, ammonium phosphates, especially ammonium hydrogenphosphate (called AHP), ammonium dihydrogen phosphate (called ADP) andpolyphosphates (especially of the metaphosphate and pyrophosphatetypes).

These ammonium salts may be pure or may include organic radicals;

phosphoric acid in its various forms, especially orthophosphoric acid(H₃PO₄), metaphosphoric acid and polyphosphoric acid ([HPO₃]);

aluminum hydrogenophosphates, especially aluminum hydrogen phosphate oraluminum dihydrogen phosphate, by themselves or mixed withorthophosphoric acid.

1. Process for producing pipe sleeves (10; 20; 30; 50) made of mineralwool for insulating pipelines or for reducing the sound level inpipeline systems, comprising the following steps: a) providing anonwoven web (11; 21; 31; 51) made of mineral wool which is providedwith an uncured binder, b) winding up the nonwoven web (11; 21; 31; 51)on a winding mandrel (2) of a winder, c) curing the binder,characterized in that at least one reinforcing layer (12, 13; 22; 32,33; 52) is provided before the nonwoven web (11; 21; 31; 51) runs intothe winder, in such a way that during the winding the said reinforcinglayer becomes a constituent part of the pipe sleeve produced as aresult.
 2. Process according to claim 1, characterized in that the atleast one reinforcing layer (22; 32, 33) is applied to the nonwoven web(21; 31) in such a way that it is wound up with it and, followingwinding, is present within the pipe sleeve (20; 30).
 3. Processaccording to claim 2, characterized in that the reinforcing layercomprises a plurality of separate strips (32, 33), which are in eachcase placed on the nonwoven web (31) and are then wound up together withthe latter.
 4. Process according to claim 1, characterized in that thereinforcing layer (13) is added to the trailing end of the nonwoven web(11) in such a way that it comes to lie on the outside of the pipesleeve (10) with the effect of a lamination, as the last layer arrangedaround the full circumference.
 5. Process according to claim 1,characterized in that the at least one reinforcing layer (12; 52) isapplied to the winding mandrel (2) before the winding of the nonwovenweb (11; 51) in such a way that it provides the inner surface of thepipe sleeve (10; 50) determining the clear internal diameter of the pipesleeve.
 6. Process according to claim 1, characterized in that thereinforcing layer (12, 13; 22; 32, 33; 52) is a glass nonwoven, a wovenglass fibre fabric, in particular made of E-glass, or the like. 7.Process according to claim 1, characterized in that the reinforcinglayer is wetted with additional binder before being provided for thewinding operation.
 8. Pipe sleeve (20; 30) made of mineral wool forinsulating pipelines or for reducing the sound level in pipelinesystems, the pipe sleeve being formed of a wound nonwoven web (21; 31)with cured binder produced by means of a process according to claim 1.9. Pipe sleeve (20; 30) made of mineral wool for insulating pipelines,the pipe sleeve being formed of a wound nonwoven web (21; 31) with curedbinder, characterized in that there is at least one reinforcing layer(22; 32, 33) on the inner side of the pipe and/or enclosed at at leastpart of the boundary between successive wound layers.
 10. Pipe sleeveaccording to claim 9, characterized in that the reinforcing layer (22;32, 33) is enclosed within the wound layers.
 11. Pipe sleeve accordingto claim 9, characterized in that the reinforcing layer (32, 33)comprises a plurality of separate strips.
 12. Pipe sleeve according toclaim 9, characterized in that a reinforcing layer (13) in the form of atrickle guard is wound circumferentially around it.
 13. Pipe sleeve (50)made of mineral wool for sound-level reduction in pipeline systems, inparticular of heating installations (40) or ventilation systems,characterized in that it has at least one reinforcing layer (52) whichprovides the inner surface of the pipe sleeve (50) that determines theclear internal diameter of the pipe sleeve.
 14. Pipe sleeve according toclaim 9, characterized in that the reinforcing layer (12, 13; 22; 32,33; 52) is a glass nonwoven, a woven glass fibre fabric or the like. 15.Pipe sleeve according to claim 9, characterized in that the reinforcinglayer includes particulate material, such as infrared radiationabsorbing material or heat shielding material.
 16. Pipe sleeve accordingto claim 9, characterized in that the reinforcing layer includes a foilmaterial, such as a heat reflective foil containing a metal likealuminum.
 17. Pipe sleeve according to claim 9, characterized in thatthe reinforcing layer is treated with a biocide agent.
 18. Pipe sleeveaccording to claim 9, characterized in that the reinforcing layer isprovided with means for allowing separation of wound layers in order toreduce external or internal diameter of the pipe.